Saturated polyester resin bottles have attracted attention, because they have the advantages that they are free from exudation of harmful materials such as a solvent from the bottles and also free from generation of harmful gases when they are burnt after the use. The bottles are molded generally by biaxial orientation so as to increase the mechanical strength of the material. However, the saturated polyester resin bottles thus prepared by biaxial orientation are apt to have residual strains on the inner walls thereof. Accordingly, if a high temperature liquid is charged in the bottles for the purpose of, for example, sterilization, a heat deformation is caused due to the strains to reduce the volume of bottles significantly. Further, when the high temperature liquid charged in the bottles is cooled, pressure in the bottles is reduced tending to also deform the same. For preventing the deformation, reinforcing ribs may be provided on the walls of the bottles, or bottles of an irregular shape which are hard to deform are employed. However, if the saturated polyester resin bottles are formed in such an irregular shape by biaxial orientation, the strains are increased even further and the heat deformation becomes worsened.